How can I prevent team killing?

I created a gun script but it allows team killing how can I edit it to remove this possibility?

Here is my code:

--player variables
local player = game.Players.LocalPlayer
local mouse = player:GetMouse()

--gun variables
local gun = script.Parent 
local ammo = 100
local magammo = ammo
local reloading = false
local auto = false -- set to false if you do not want the gun to be automatic
local firing = false
local CanChangeFireModes = false
local damage = 80, 100
--^^If set to true the player can press v to change firemodes from auto to semi and semi to auto

local debounce = false

if not game.workspace:FindFirstChild("Bullet") then
    local bullet_storage = Instance.new("Folder", workspace)
    bullet_storage.Name = "Bullet"
else
    --nothing
end

function getBullet()
    print(ammo)
    if ammo > 0 then
        if debounce == false then
            debounce = true
            ammo = ammo - 1
            gun.Handle.Fire:Play()
            local mh = mouse.Hit
            local B = Instance.new("Part", workspace.Bullet)
            B.CFrame = gun.Handle.CFrame + (player.Character.Torso.CFrame.lookVector)
            B.CFrame = CFrame.new(B.Position, mh.p)
            B.FormFactor = "Custom"
            B.Size = Vector3.new(0.2, 0.2, 0.2)
            B.BrickColor = BrickColor.Black()
            B.CanCollide = false
            local velo = Instance.new("BodyVelocity", B)
            velo.velocity = B.CFrame.lookVector * 120
            velo.maxForce = Vector3.new(math.huge, math.huge, math.huge)
            B.Touched:connect(function(hit)
                local humanoid = hit.Parent:FindFirstChild("Humanoid")
                if humanoid then
                    humanoid:TakeDamage(damage)
                end
            end)
        wait(0)
        debounce = false
        end
    end
end

function autofire()
    if ammo > 0 then
        while firing == true do
            if firing == true and ammo <= 0 then
                firing = false
            end
            print(ammo)
            wait(0)
            gun.Handle.Fire:Play()
            local mh = mouse.Hit
            local B = Instance.new("Part", workspace.Bullet)
            B.CFrame = gun.Handle.CFrame + (player.Character.Torso.CFrame.lookVector)
            B.CFrame = CFrame.new(B.Position, mh.p)
            B.FormFactor = "Custom"
            B.Size = Vector3.new(0.2, 0.2, 0.2)
            B.BrickColor = BrickColor.Black()
            B.CanCollide = false
            ammo = ammo - 1
            local velo = Instance.new("BodyVelocity", B)
            velo.velocity = B.CFrame.lookVector * 120
            velo.maxForce = Vector3.new(math.huge, math.huge, math.huge)
            B.Touched:connect(function(hit)
                local humanoid = hit.Parent:FindFirstChild("Humanoid")
                if humanoid then
                    humanoid:TakeDamage(damage)
                end
            end)
        wait(0.005)
        end
    end
end

mouse.Button1Down:connect(function()
    if auto == true then
        firing = true
        autofire()
    else
        getBullet()
    end
    if ammo <= 0 then
        print('reloading')
        wait(2)
        ammo = magammo
    end
end)

mouse.Button1Up:connect(function()
    if firing == true then
        firing = false
    end
end)

local uis = game:GetService("UserInputService") -- allows firemode change
uis.InputBegan:connect(function(inputObject, gameProcessedEvent)
    if inputObject.KeyCode == Enum.KeyCode.V and CanChangeFireModes == true then
        if auto == true then
            auto = false
        else
            auto = true
        end
    end
end)